Method of producing multiple microstructure components

ABSTRACT

Methods are provided for manufacturing turbine disks each having a hub surrounded by a rim, the hub having a first microstructure and the rim having a second microstructure that is coarser than the first microstructure, the methods employing a first powder alloy having a first gamma prime solvus temperature and a second powder alloy having a second gamma prime solvus temperature that is less than the first gamma prime solvus temperature. One method includes the steps of forming an ingot from the first and second powder alloys, the ingot having an inner section having the first microstructure and an outer section having a microstructure that is less coarse than the second microstructure, and exposing the ingot to a temperature between the first and second gamma prime solvus temperatures while forming the ingot into a plurality of turbine disks to transform the microstructure of the outer section into the second microstructure.

TECHNICAL FIELD

The present invention relates to turbine disks and, more particularly, to turbine disks that are multiple microstructure components.

BACKGROUND

During operation of a gas turbine engine, a disk that supports a plurality of turbine blades typically rotates at high speeds in a high temperature environment. In many cases, a hub portion of the disk is exposed to temperatures of about 1000° F., while a rim portion of the disk is exposed to higher temperatures, such as about 1500° F. or higher. Because of the differences in operating conditions, the hub and rim are preferably formed of alloys having different properties. For example, hubs have been formed from alloys having high tensile strength and high resistance to low cycle fatigue, while rims have been formed from alloys having high stress rupture and creep resistance.

Several techniques currently exist for constructing dual alloy turbine wheel hubs. However, each suffers from certain drawbacks. For example, one technique includes metallurgically bonding an inner hub preform to a rim preform and isothermally forging the two together. Although such a technique yields acceptable disks, only one disk may be produced from the two preforms. Another technique involves forming a disk preform having a first grain structure and using specialized equipment to heat an outer periphery of the disk structure to obtain a second grain microstructure. However, such equipment is relatively expensive and thus, the technique is costly to implement. Still another technique uses a conventionally cast ingot that is extruded or hot isostatically pressed to yield an ingot having an inner and an outer region, each having a different grain microstructure. However, the boundary, location, and shape of the first and second regions may be imprecise.

Thus, there is a need for a method for forming a dual alloy turbine wheel hub that is relatively inexpensive and that utilizes conventional equipment. Additionally, there is a need for a method that can be used to form more than one turbine wheel hub.

BRIEF SUMMARY

The present invention provides methods for manufacturing turbine disks each having a hub surrounded by a rim, the hub having a first microstructure and the rim having a second microstructure that is coarser than the first microstructure, the method employing a first powder alloy having a first gamma prime solvus temperature and a second powder alloy having a second gamma prime solvus temperature that is less than the first gamma prime solvus temperature.

In one embodiment, and by way of example only, the method includes the steps of forming an ingot from the first and second powder alloys, the ingot having an inner section having the first microstructure and an outer section having a microstructure that is less coarse than the second microstructure, and exposing the ingot to a temperature between the first and second gamma prime solvus temperatures while forming the ingot into a plurality of turbine disks to transform the microstructure of the outer section into the second microstructure.

In another embodiment, and by way of example only, a method is provided for manufacturing a turbine disk having a hub surrounded by a rim, the hub having a first microstructure and the rim having a second microstructure that is coarser than the first microstructure, the method employing a first powder alloy having a first gamma prime solvus temperature and a second powder alloy having a second gamma prime solvus temperature that is less than the first gamma prime solvus temperature. The method comprises the steps of forming an ingot from the first and second powder alloys, the ingot having an inner section having the first microstructure and an outer section having the second microstructure, and exposing the ingot to a temperature below the first gamma prime solvus temperature while forming the ingot into a plurality of turbine disks.

Other independent features and advantages of the preferred methods will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an exemplary turbine disk;

FIG. 2 is a cross-sectional view of an ingot that may be used in a process for manufacturing the turbine disk depicted in FIG. 1; and

FIGS. 3-7 are flow diagrams of exemplary methods by which to manufacture the exemplary turbine disk depicted in FIG. 1

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention.

Turning now to FIG. 1, a cross section of an exemplary turbine disk 100 is provided. The turbine disk 100 includes a hub 102 and a rim 104, each having different material properties. The hub 102 is configured to have high tensile strength and high resistance to low cycle fatigue. In this regard, the hub 102 preferably has a fine-grained microstructure comprising grains that are between about 5 microns and about 10 microns in size. The rim 104 is configured to have high stress rupture and creep resistance and preferably has a coarse-grained microstructure. The coarse-grained microstructure preferably has grains that are between about 15 microns and about 30 microns in size.

To form the turbine disk 100, generally, first an ingot 200, shown in FIG. 2, is formed and sliced into disks, and the disk is then machined into the turbine disk 100. Preferably, the ingot 200 includes an inner section 202 having a first material property and an outer section 204 having a second material property. The inner section 202 is a solid rod, while the outer section is an annular cylinder. Most preferably, the inner section 202 has a fine-grained microstructure and the outer section 204 has a coarse-grained structure, and the two sections 202, 204 are metallurgically bonded to each other.

The ingot 200 and turbine disk 100 may be formed using any one of the following methods. It will be appreciated that in each of the following methods, two powder alloys are used. Each powder alloy includes a gamma phase component and a gamma prime phase component, where the gamma phase component is a metal matrix and the gamma prime phase component is a precipitate that is held in solution within the metal matrix when the first powder alloy phase changes into a solid. Each gamma prime phase component preferably has a different temperature at which it enters into solution, and heat treatment above that temperature results in grain growth. In the methods described below, a gamma prime solvus temperature T_(A) of the first powder alloy is greater than a gamma prime solvus temperature T_(B) of the second powder alloy.

It will be appreciated that any one of numerous suitable powder alloys conventionally used in the formation of turbine disks may be employed. For example, two chemical variations of a single alloy, such as Alloy 10 produced by Honeywell, Inc. of Morristown, N.J. may be used. In this embodiment, a first variation may include 18.5 wt. % Cr, while a second variation may includes 19.5 wt % Cr. Other suitable powder alloys that include, but are not limited to Rene 95, low carbon Astroloy, and Alloy 720 may alternatively be used.

One exemplary method 300, shown in FIG. 3, includes the steps of depositing the first powder alloy into a first volume, step 302. The first powder alloy is pressurized at a temperature below T_(A) to form a first component, step 304. A second powder alloy is deposited into a second volume configured to be adjacent the first section, step 306. The second powder alloy is pressurized at a temperature above T_(B) to form a second component, step 308. Then, the first and second components are containerized, step 310, and pressurized at a temperature below T_(A), to form the ingot 200, step 312. The ingot 200 is processed at a temperature below T_(A) to form the turbine disk 100, step 314.

As briefly mentioned above, the first powder alloy is deposited into a first volume, step 302. Preferably, the first volume is configured to have the shape of the inner section 202 of the ingot 200 and is contained in a suitably shaped space of a container. Thus, for example, the container may be a hollow cylinder. The container is preferably constructed of any one of numerous suitable materials capable of withstanding temperatures of at least 2000° F. to allow the first powder alloy to solidify into a desired shape.

After deposition, the first powder alloy is then pressurized at a temperature below its gamma prime solvus temperature, T_(A), step 304. Preferably, the powder alloy is pressurized at a pressure of between about 10 ksi and about 30 ksi. Consequently, the first powder alloy transforms into the first component having a fine grain microstructure, where each grain size is between about 5 microns and about 10 microns. In an embodiment in which the first powder alloy is deposited into a hollow cylinder, the first section is formed into a solid rod.

The second powder alloy is deposited into a second volume, step 306. In one exemplary embodiment, the second volume is contained in a container shaped similarly to the outer section 204 of the ingot 200. In this regard, the container may be an annular tube having an outer annular space separated from an inner space sized to receive the first component. In another exemplary embodiment, the container has any shape.

The second powder alloy is pressurized at a temperature above its gamma prime solvus temperature, T_(B), step 308, to form the second component. Preferably, the powder alloy is pressurized at a pressure of between about 10 ksi and about 30 ksi. As a result, the second powder alloy transforms into a solid having a coarse grain microstructure with grain sizes of between about 15 microns and about 30 microns.

After the first and second components are formed, they are containerized in a single container, step 310. In one embodiment of method 300, the first and second components are machined into appropriate shapes before containerization. If needed, the first component is machined into the shape of the ingot inner section 202, for example, a rod, while the second section is formed into the shape of the ingot outer section 204, for example, an annular cylinder having a suitably sized rod-shaped shape therein. During containerization, the first component is nested in the space of the second component.

Next, the first and second components are pressurized at a temperature below T_(A), step 312. During this step, the first and second components are subjected to a pressure of between about 10 ksi and about 30 ksi and are metallurgically bond to each other to form the ingot 200. While maintaining a temperature below T_(A), the ingot 200 is then processed to form the turbine disk 100, step 314. Specifically, the ingot 200 is sliced, machined, and/or heat-treated.

It will be appreciated that although these steps 302, 304, 306, 308, 310, 312, 314 are discussed above in a specific sequence, they may be performed in any other suitable sequence.

Another exemplary method 400 for forming the turbine disk 100, is depicted in FIG. 4. In this method 400, the first and second powder alloys are first deposited into a container containing the first and second volumes, respectively, step 402. Preferably, the container includes a generally cylindrical outer wall that defines a space therein and a generally cylindrical inner wall that divides the space into an outer section and an inner section. The inner wall may have any one of numerous suitable configurations. In one exemplary embodiment, the inner wall is an interleaf. The first powder alloy is deposited in the inner section of the container, and the second powder alloy is deposited in the outer section. In an embodiment in which the container includes an interleaf, the interleaf is removed after the container is sufficiently filled.

In one exemplary embodiment of method 400, the powder alloys in the container are pressurized at a temperature below TB, step 404. Preferably, the powder alloys are pressurized at a pressure of between about 10 ksi and about 30 ksi. As a result, the first and second powder alloys solidify and metallurgically bond together to form the inner and outer sections 202, 204 of the ingot 200, respectively. The inner and outer sections 202, 204 each have a fine-grained microstructure. It will be appreciated that the pressurization of the powder alloys may be performed in any one of numerous manners. For example, the powder alloys may be extruded from a container having a first diameter through a container having a second, smaller diameter, step 406. In either case, the ingot 200 is further processed, for example, sliced, machined, and/or heat treated to form the turbine disk 100 at a temperature that is between T_(A) and T_(B), step 408. Consequently, grain growth occurs in the outer section 204, but does not occur in the inner section 202 to thereby yield a coarse-grained microstructure and fine-grained microstructure, respectively.

In another exemplary embodiment of the method 400, the powder alloys in the container are pressurized at a temperature that is between T_(A) and T_(B), step 410. Preferably, the powder alloys are pressurized at a pressure of between about 10 ksi and about 30 ksi. The first and second powder alloys solidify to form the inner and outer sections 202, 204 of the ingot 200, respectively, where the inner section 202 has a fine-grained microstructure and the outer section 204 has a coarse-grained microstructure. Additionally, the inner and outer sections 202, 204 are metallurgically bonded to form the ingot 200. Next, the ingot 200 is further processed, for example, sliced, machined, and/or heat treated, step 412. Preferably, the processing is performed at a temperature that is below T_(A) to maintain the fine-grained microstructure of the inner section 202 and the coarse-grained microstructure of the outer section 204.

FIG. 5 shows another exemplary method 500 for forming the turbine disk 100. In this embodiment, the first powder alloy is deposited into a container that contains the first volume, step 502. The first powder alloy is then pressurized at a temperature below T_(A), step 504, preferably, at a pressure of between about 10 ksi and about 30 ksi. Consequently, the first powder alloy solidifies and forms a first component having a fine-grained microstructure. Optionally, the first component is machined into an appropriate shape, for example, into a rod, step 506. Next, the second powder alloy and the first component are containerized, step 508. Preferably, the first component is placed into substantially the middle of a container, and the second powder alloy is deposited into the container around the first component.

In one exemplary embodiment of method 500, the containerized first component and second powder alloy are pressurized at a temperature below T_(B), step 510. Preferably, pressurization occurs at between about 10 ksi and about 30 ksi. As a result, the second powder alloy solidifies and forms the second component. The second component, which surrounds the first component, metallurgically bonds thereto to form the ingot 200. Additionally, the second component transforms into a fine-grained microstructure. The ingot 200 is then further processed into the turbine disk 100 at a temperature between T_(A) and T_(B), step 512. Consequently, the outer section 204 experiences grain growth to form a coarse-grained microstructure, while the inner section 202 maintains a fine-grained structure.

In an alternate embodiment of method 500, the containerized first component and second powder alloy are pressurized at a temperature between T_(A) and T_(B), step 514, after the containerization step 508. Preferably, pressurization occur at between about 10 ksi and about 30 ksi. During this step, the second powder alloy solidifies and forms the second component, and the first and second components metallurgically bond to form the ingot 200 having the inner and outer sections 202, 204. In this embodiment, the inner section 202 has a fine-grained microstructure, while the outer section 204 has a coarse-grained microstructure. The ingot 200 is then processed into the turbine disk 100 at a temperature that is below T_(A), step 516, so that the microstructures of the inner and outer sections 202, 204 are maintained.

FIGS. 6 and 7 each illustrate other methods 600, 700 for manufacturing the ingot 200, where the second powder alloy is solidified before the first powder alloy. In method 600, the second powder alloy is first deposited into a suitably shaped container containing the second volume, step 602. Then, the second powder alloy is pressurized at a temperature below T_(B), step 604, so that the formed second component has a fine-grained microstructure. Preferably, pressurization occurs at a pressure that is between about 10 ksi and about 30 ksi. If needed, the second component is then machined, step 606, into a shape similar to that of the ingot outer section 204 (i.e., a hollow cylinder having a space in the middle thereof). Next, the first powder alloy and the second component are containerized, step 608. In one exemplary embodiment, the second component is placed into a container and the first powder alloy is deposited into the space of the second component.

In one exemplary embodiment of method 600, the containerized second component and first powder alloy are pressurized at a temperature between T_(A) and T_(B), step 610. Preferably, pressurization occurs at a pressure that is between about 10 ksi and about 30 ksi. As a result, the first powder alloy solidifies and forms the first component having a coarse-grained microstructure. Additionally, the second component maintains a fine-grained microstructure. Moreover, the first and second components metallurgically bond to each other and form the ingot 200. The ingot 200 is then processed, for example, sliced, machined, and/or heat-treated, at a temperature that is below T_(B) to form the turbine disk 100, step 612.

In an alternate embodiment of method 600, after step 608, the containerized second component and first powder alloy are pressurized at a temperature below T_(B), step 614. Preferably, pressurization occurs at a pressure that is between about 10 ksi and about 30 ksi. In this case, the first powder alloy phase changes into a solid first component and metallurgically bonds to the second component to form the ingot 200. However, both the ingot inner and outer sections 202, 204 have fine-grained microstructures. After step 614, the ingot 200 is processed at a temperature of between T_(A) and T_(B), step 616, and as a result, the inner section 202 maintains a fine-grained microstructure, while the outer section 204 experiences grain growth and forms a coarse-grained microstructure.

FIG. 7 shows still yet another method 700 for forming the turbine disk 100. In this embodiment, the second powder alloy is deposited into a suitably shaped container containing the second volume, step 702. Then, the second powder alloy is pressurized at a temperature above T_(B), step 704, causing the second powder alloy to solidify and form a second component having a coarse-grained microstructure. Preferably, pressurization occurs at a pressure that is between about 10 ksi and about 30 ksi. If needed, the second component is then machined into the shape of the ingot outer section 204, step 706. As a result, the second component is machined into a hollow cylinder.

After step 706, the second component and first powder alloy are containerized, step 708. Preferably, the second component is positioned in a suitable container and the first powder alloy is deposited into the hollow section of the second component. The containerized second component and first powder alloy are pressurized at a temperature between T_(A) and T_(B), step 710. Preferably, pressurization occurs at a pressure that is between about 10 ksi and about 30 ksi. In this regard, the first powder alloy solidifies to form the first component and the first and second components metallurgically bond to each other to form the ingot 200. The pressurization step causes the grains in the ingot outer section 204 to grow into a coarse-grained microstructure, while the ingot inner section 202 has a fine-grained microstructure. Subsequently, the ingot 200 is further processed into the turbine disk 100 at a temperature below T_(A), step 712. Thus, while the ingot 200 is being sliced, machined, and/or heat-treated, the fine-grained microstructure of the inner section 202 and the coarse-grained microstructure of the outer section 204 are maintained.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. 

1. A method of manufacturing turbine disks each having a hub surrounded by a rim, the hub having a first microstructure and the rim having a second microstructure that is coarser than the first microstructure, the method employing a first powder alloy having a first gamma prime solvus temperature and a second powder alloy having a second gamma prime solvus temperature that is less than the first gamma prime solvus temperature and comprising the steps of: forming an ingot from the first and second powder alloys, the ingot having an inner section having the first microstructure and an outer section having a microstructure that is less coarse than the second microstructure; and exposing the ingot to a temperature between the first and second gamma prime solvus temperatures while forming the ingot into a plurality of turbine disks to transform the microstructure of the outer section into the second microstructure.
 2. The method of claim 1, wherein the step of forming the ingot comprises: containerizing the first and the second powder alloys in a container having a first volume and a second volume surrounding the first volume, respectively; pressurizing the first and second powder alloys at a pressure of between about 10 ksi and about 30 ksi at a temperature below the second gamma prime solvus temperature to form the inner and outer sections of the ingot, respectively.
 3. The method of claim 2, wherein the container has a first diameter and the method further comprises extruding the first and second powder alloys through a second container having a second diameter that is smaller than the first diameter.
 4. The method of claim 1, wherein the first microstructure has a plurality of grains each having a grain size of between about 5 microns and about 10 microns and the second microstructure has a plurality of grains each having a grain size of between about 15 microns and about 30 microns.
 5. The method of claim 1, wherein the step of forming the ingot comprises: depositing the first powder alloy into a first volume; pressurizing the first powder alloy at a pressure of between about 10 ksi and about 30 ksi at a temperature below the first gamma prime solvus temperature to form a first component; depositing the second powder alloy into a second volume configured to surround the first volume; pressurizing the second powder alloy at a pressure of between about 10 ksi and about 30 ksi at a temperature below the second gamma prime solvus temperature to form a second component; containerizing the first and the second components such that the first component is surrounded by the second component; and pressurizing the containerized first and second components at a pressure of between about 10 ksi and about 30 ksi at a temperature below the first gamma prime solvus temperature to form the ingot, wherein the first and second components transform into the inner and outer sections of the ingot, respectively.
 6. The method of claim 5, further comprising: machining the first component into a rod; and machining the second component into a cylinder.
 7. The method of claim 1, wherein the step of forming the ingot comprises: depositing the first powder alloy into a first volume; pressurizing the first powder alloy at a pressure of between about 10 ksi and about 30 ksi while exposed to a temperature below the first gamma prime solvus temperature to form a first component having the first microstructure; and containerizing the first component and the second powder alloy, wherein the second powder alloy surrounds the first component; and pressurizing the containerized first component and second powder alloy at a pressure of between about 10 ksi and about 30 ksi at a temperature below the second gamma prime solvus temperature to transform the first component into the ingot inner section and the second powder alloy into the ingot outer section.
 8. The method of claim 1, wherein the step of forming the ingot comprises: depositing the second powder alloy into a volume; pressurizing the second powder alloy at a pressure of between about 10 ksi and about 30 ksi while exposed to a temperature below the second gamma prime phase solvus temperature to form a component having a microstructure that is less coarse than the second microstructure; and containerizing the second powder alloy component and the first powder alloy, wherein the first powder alloy surrounds the second powder alloy component; and pressurizing the containerized second powder alloy component and first powder alloy at a pressure of between about 10 ksi and about 30 ksi at a temperature below the second gamma prime phase solvus temperature to transform the second powder alloy component into the ingot outer section and the first powder alloy into the ingot inner section.
 9. The method of claim 1, wherein the step of exposing further comprises: slicing the ingot into a plurality of disks; and machining one disk of the plurality of disks into the turbine disk.
 10. A method of manufacturing a turbine disk having a hub surrounded by a rim, the hub having a first microstructure and the rim having a second microstructure that is coarser than the first microstructure, the method employing a first powder alloy having a first gamma prime solvus temperature and a second powder alloy having a second gamma prime solvus temperature that is less than the first gamma prime solvus temperature and comprising the steps of: forming an ingot from the first and second powder alloys, the ingot having an inner section having the first microstructure and an outer section having the second microstructure; and exposing the ingot to a temperature below the first gamma prime solvus temperature while forming the ingot into a plurality of turbine disks.
 11. The method of claim 10, wherein the step of forming the ingot comprises: containerizing the first and the second powder alloys in a container having a first volume and a second volume surrounding the first volume, respectively; pressurizing the first and second powder alloys at a pressure of between about 10 ksi and about 30 ksi at a temperature between the first and the second gamma prime solvus temperatures to form the inner and outer sections of the ingot, respectively.
 12. The method of claim 10, wherein the first microstructure has a plurality of grains each having a grain size of between about 5 microns and about 10 microns and the second microstructure has a plurality of grains each having a grain size of between about 15 microns and about 30 microns.
 13. The method of claim 10, wherein the step of forming the ingot comprises: depositing the first powder alloy into a first volume; pressurizing the first powder alloy at a pressure of between about 10 ksi and about 30 ksi at a temperature below the first gamma prime solvus temperature to form a first component; containerizing the first component and the second powder alloy such that the second powder alloy surrounds the first component; and pressurizing the containerized first component and second powder alloy at a pressure of between about 10 ksi and about 30 ksi at a temperature between the first and second gamma prime solvus temperatures to transform the first component into the ingot inner section and the second powder alloy into the ingot outer section.
 14. The method of claim 13, further comprising: machining the first component into a rod; and machining the second component into a cylinder.
 15. The method of claim 10, wherein the step of forming the ingot comprises: depositing the second powder alloy into a volume; pressurizing the second powder alloy at a pressure of between about 10 ksi and about 30 ksi at a temperature that is below the second gamma prime solvus temperature to form a component; containerizing the second powder alloy component and the first powder alloy, wherein the second powder alloy component surrounds the first powder alloy; and pressurizing the containerized second powder alloy component and first powder alloy at a pressure of between about 10 ksi and about 30 ksi at a temperature between the first and second gamma prime solvus temperatures to transform the second powder alloy component into the ingot inner section and the second powder alloy into the ingot outer section.
 16. The method of claim 10, wherein the step of forming the ingot comprises: depositing the second powder alloy into a second volume; pressurizing the second powder alloy at a pressure of between about 10 ksi and about 30 ksi at a temperature that is above the second gamma prime solvus temperature to form a component; containerizing the second powder alloy component and the first powder alloy, wherein the second powder alloy component surrounds the first powder alloy; and pressurizing the containerized second powder alloy component and first powder alloy at a pressure of between about 10 ksi and about 30 ksi at a temperature between the first and second gamma prime solvus temperatures to transform the second powder alloy component into the ingot inner section and the second powder alloy into the ingot outer section.
 17. The method of claim 16, further comprising: machining the first component into a rod; and machining the second component into a cylinder.
 18. The method of claim 10, wherein the step of exposing further comprises: slicing the ingot into a plurality of disks; and machining one disk of the plurality of disks into the turbine disk. 